Re: ELCAN SpecterDR 1.5x6 for 50BMG ?
From Ratheon website:
SpecterDR 1.5-6x™
The SpecterDR™ by ELCAN is a revolutionary optical design that combines the best of close combat and precision fire ranging features into a single, low profile dual-field-of view (DFOV) sight. SpecterDR 1.5-6x, with its dual-role capability gives machine gun operators and designated marksmen a sweeping 1.5x view of the battlefield for target acquisition, then allows instant switching to 6x for accurate, long range precision fire and suppression.
Situational awareness in both magnifications is improved with wider viewing angles and unmatched light transmission in low light conditions. SpecterDR™ 1.5-6x can be ordered with 5.56, 7.62 or .50Cal variable illuminated night vision compatible reticles as well. SpecterDR™ 1.5-6x Specifications
http://www.elcansightingsystems.com/products/dual_role_sights.php
Read the last paragraph, says its possible.
I have never seen one in real life before (the 50 bmg reticle).
I run a 1.5-6x 7.62 and I am very familiar with the product.
The models you have look odd. In my opinion they are older models (due to the logo's on the side), prototypes (due to the mis- coloration of the lens frame to the body frame) or FAKES. Also on the current 1.5-6x models the optic bell and body are 1 piece. Not separate like the 4x versions. The 50 bmg reticle is not and option in the 4x frame, only the larger 1.5-6x frame.
Without having them in my hand I could not be for sure.
Look at this:
http://www.elcansightingsystems.com/Main/pdf/SpecterDR1.5-6x.OPM002RevC.Manual.pdf.pdf
That is exactly how my Elcan looks. Yours look like the 1-4x model with a bigger bell. To me this confirms my earlier thoughts (prototype, older model or sadly FAKE).
Again though, the 50 BMG reticle is an option.
Good luck.